The long term commercial potential of producing useful products by photosynthesis techniques using simple plant matter, such as algae and seaweed, has been recognised for some time. Indeed the ability of simple single cell organisms, such as blue green algae, to utilise sunlight, carbon dioxide and the inorganic constituents of sea water to produce more complex matter played an essential part in the evolutionary process. Many attempts have been made to harness the ability of simple organisms to produce complex materials.
Open channel cultivation of algae has been attempted to produce a biomass for animal or human consumption. Not surprisingly this comparatively crude method has proved impracticable for production of pure high grade products because of such problems as invasion by hostile species (sometimes producing dangerous toxins), other pollution (such as dust), difficulty in the control of such variables as nutrient ratios, temperature and pH, intrinsically low yield because of escape of carbon dioxide to the atmosphere and inefficient use of light to illuminate only the top portion of the biomass.
Somewhat more sophisticated attempts have involved the use of horizontally disposed large diameter transparent plastics tubes for biomass production, e.g. Italian Patent Application No. 21522 A/78. The problems of such a system include the low density of biomass in the liquid within the tubes, coating of the pipes by algae due to low velocity flow therethrough thus reducing transparency, overheating in summer weather and high land usage.
As an alternative, a construction has been proposed in U.K. Patent No. 2118572 comprising flat vertical panels, (of area about 1 square meter) having a pipe of comparatively small diameter wound substantially horizontally against the panel face thereof. Again the land usage is high, in that each square meter of plant requires a square meter of ground area for its installation. Furthermore, the process control problems of manipulating a sufficiently large number of such units for commercial production are enormous. The design of the panels gives an inherently unstable construction unable to withstand adverse weather conditions.
Other problems encountered include the growth of unwanted microscopic species, such as bacteria, amoeba and rotifers within the biomass culture, particularly when operating in open cultures.